Exotic physics phenomenon is observed for first time

An exotic physical phenomenon, involving optical waves, synthetic magnetic fields, and time reversal, has been directly observed for the first time, following decades of attempts. The new finding could lead to realizations of what are known as topological phases, and eventually to advances toward fault-tolerant quantum computers, the researchers say.

The new finding involves the non-Abelian Aharonov-Bohm Effect and is reported today in the journal Science by MIT graduate student Yi Yang, MIT visiting scholar Chao Peng (a professor at Peking University), MIT graduate student Di Zhu, Professor Hrvoje Buljan at University of Zagreb in Croatia, Francis Wright Davis Professor of Physics John Joannopoulos at MIT, Professor Bo Zhen at the University of Pennsylvania, and MIT professor of physics Marin Soljacic.

The finding relates to gauge fields, which describe transformations that particles undergo. Gauge fields fall into two classes, known as Abelian and non-Abelian. The Aharonov-Bohm Effect, named after the theorists who predicted it in 1959, confirmed that gauge fields—beyond being a pure mathematical aid—have physical consequences.

But the observations only worked in Abelian systems, or those in which gauge fields are commutative—that is, they take place the same way both forward and backward in time. In 1975, Tai-Tsun Wu and Chen-Ning Yang generalized the effect to the non-Abelian regime as a thought experiment. Nevertheless, it remained unclear whether it would even be possible to ever observe the effect in a non-Abelian system. Physicists lacked ways of creating the effect in the lab, and also lacked ways of detecting the effect even if it could be produced. Now, both of those puzzles have been solved, and the observations carried out successfully.

The effect has to do with one of the strange and counterintuitive aspects of modern physics, the fact that virtually all fundamental physical phenomena are time-invariant. That means that the details of the way particles and forces interact can run either forward or backward in time, and a movie of how the events unfold can be run in either direction, so there's no way to tell which is the real version. But a few exotic phenomena violate this time symmetry.

Creating the Abelian version of the Aharonov-Bohm effects requires breaking the time-reversal symmetry, a challenging task in itself, Soljacic says. But to achieve the non-Abelian version of the effect requires breaking this time-reversal multiple times, and in different ways, making it an even greater challenge.

To produce the effect, the researchers use photon polarization. Then, they produced two different kinds of time-reversal breaking. They used fiber optics to produce two types of gauge fields that affected the geometric phases of the optical waves, first by sending them through a crystal biased by powerful magnetic fields, and second by modulating them with time-varying electrical signals, both of which break the time-reversal symmetry. They were then able to produce interference patterns that revealed the differences in how the light was affected when sent through the fiber-optic system in opposite directions, clockwise or counterclockwise. Without the breaking of time-reversal invariance, the beams should have been identical, but instead, their interference patterns revealed specific sets of differences as predicted, demonstrating the details of the elusive effect.

The original, Abelian version of the Aharonov-Bohm effect "has been observed with a series of experimental efforts, but the non-Abelian effect has not been observed until now," Yang says. The finding "allows us to do many things," he says, opening the door to a wide variety of potential experiments, including classical and quantum physical regimes, to explore variations of the effect.

The experimental approach devised by this team "might inspire the realization of exotic topological phases in quantum simulations using photons, polaritons, quantum gases, and superconducting qubits," Soljacic says. For photonics itself, this could be useful in a variety of optoelectronic applications, he says. In addition, the non-Abelian gauge fields that the group was able to synthesize produced a non-Abelian Berry phase, and "combined with interactions, it may potentially one day serve as a platform for fault-tolerant topological quantum computation," he says.

At this point, the experiment is primarily of interest for fundamental physics research, with the aim of gaining a better understanding of some basic underpinnings of modern physical theory. The many possible practical applications "will require additional breakthroughs going forward," Soljacic says.

For one thing, for quantum computation, the experiment would need to be scaled up from one single device to likely a whole lattice of them. And instead of the beams of laser light used in their experiment, it would require working with a source of single individual photons. But even in its present form, the system could be used to explore questions in topological physics, which is a very active area of current research, Soljacic says.

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User comments

"The effect has to do with one of the strange and counterintuitive aspects of modern physics, the fact that virtually all fundamental physical phenomena are time-invariant. That means that the details of the way particles and forces interact can run either forward or backward in time, and a movie of how the events unfold can be run in either direction, so there's no way to tell which is the real version. But a few exotic phenomena violate this time symmetry."

Time-reversal indeed!! WHERE do these scientists get these hare-brained ideas from? A movie?? Is that an 'indy' movie or one from a big-name studio like MGM? A MOVIE can be run forward or reverse, but REALITY is not a movie.EVENTS and ACTIONS do NOT run in either direction. They can ONLY go-flow-stream FORWARD. IF events/actions were able to reverse/go backward, the whole FUTURE would be altered to such a degree that the Universe and all that is in it would become chaotic and eventually break down completely.

"For one thing, for quantum computation, the experiment would need to be scaled up from one single device to likely a whole lattice of them. And instead of the beams of laser light used in their experiment, it would require working with a source of single individual photons."

Quantum Computation seems to be a very relevant undertaking. But why would these scientists say that Particles, eg are reversing? In a Clock that is run by Cs133 Electrons, the Electrons are jumping forward and backward but are NOT reversing in 'time'/Events-Actions. Even when something or someone is walking backwards, they are STILL going forward.

Always interesting when a time asymmetry is proven. This one has been conjectured for a long time and it's good to see it confirmed. We can add this to the B-, D-, and k-mesons (also called kaons) as an example of broken time-reversal symmetry, and since it's in the EM force we can now see two of the four forces displaying time asymmetry: weak and EM. Interestingly, these two forces both originate from the electroweak force of Weinberg and Salam, indicating that we have much more to find out about this aspect of QM. There's new physics here somewhere.

Always interesting when a time asymmetry is proven. This one has been conjectured for a long time and it's good to see it confirmed. We can add this to the B-, D-, and k-mesons (also called kaons) as an example of broken time-reversal symmetry, and since it's in the EM force we can now see two of the four forces displaying time asymmetry: weak and EM. Interestingly, these two forces both originate from the electroweak force of Weinberg and Salam, indicating that we have much more to find out about this aspect of QM. There's new physics here somewhere.

Whenever I see new physics, or even the possibility of new physics, I get jolly-well fired up and genuinely excited! And whenever there's new physics, there's new mathematics, too.

"Creating the Abelian version of the Aharonov-Bohm effects requires breaking the time-reversal symmetry, a challenging task in itself"Not so sure this is true. One could hold onto chirality, for a timeless communicative theory.An infinite abelian group, lacks clarity, so it possesses relative entropic reversibility, for all intensive purposes.Easier to not necessitate error-correcting code, via a reduction of unitarity, eh?

Think it will be found that time reversals really do take place. However it will also be found that time is three dimensional in any given 6 dim subset of the 11 dimensional conjectured superspace universe exterior to our universe. That is three dimensions of space and three of time. The constraint is that one can go back in time EXCEPT not on a congruent path to ones own past, however discontinuous. So you CAN go back in time but on OTHER timelines. In any case, your future is one of an "Infinity of Mirrors"! Traverse to it you may; go back on the same path you traversed you may not. You could meet time travelers in any instant of space-time you may occupy, past, present, or future. You really only really HAVE the present. Maybe that makes sense to you or maybe not, but like the old boy said, The universe is not only stranger than we think, but strains our ability to imagine as well. See you in infinity, Northern continent, ProximaCentauri 3

Or you know, we are engines of confabulation as assumptions are intrinsic to neuromorphic hyper compuation, and the social construct favors a theory of potential curls, taken invariant, that exhibit functionalist pragmatics.As the answer ancient question of connected or disconnect, is neither. You are psychotic. At least be practical.

Think it will be found that time reversals really do take place. However it will also be found that time is three dimensional in any given 6 dim subset of the 11 dimensional conjectured superspace universe exterior to our universe. That is three dimensions of space and three of time. The constraint is that one can go back in time EXCEPT not on a congruent path to ones own past, however discontinuous. So you CAN go back in time but on OTHER timelines. In any case, your future is one of an "Infinity of Mirrors"! Travers to it you may; go back on the same path you traversed you may not. You could meet time travelers in any instant of space-time you may occupy, past, present, or future. You really only really HAVE the present. Maybe that makes sense to you or maybe not, but like the old boy said, The universe is not only stranger than we thing, but strains our ability to imagine as well. See you in infinity, Northern continent, ProximaCentauri 3

Always interesting when a time asymmetry is proven. This one has been conjectured for a long time and it's good to see it confirmed. We can add this to the B-, D-, and k-mesons (also called kaons) as an example of broken time-reversal symmetry, and since it's in the EM force we can now see two of the four forces displaying time asymmetry: weak and EM. Interestingly, these two forces both originate from the electroweak force of Weinberg and Salam, indicating that we have much more to find out about this aspect of QM. There's new physics here somewhere.

@Da SchneibIt is always nice to read your knowledgeable posts. Like a swan in a quivering duck pond, you have a higher perspective and look over the reeds.

Rationally minded people do not take seriously implications of time reversal, but this chatroom full of overage Trekkies is a different matter, right Schneibo?

Its not that they do not take it seriously, it is that they find determinism more interesting than a potential energetic completeness, trying to abuse the assumptions of the model they are bringing, rather than the shift in perspective, as it is demonstrated.

Quantum Computation seems to be a very relevant undertaking. But why would these scientists say that Particles, eg are reversing? In a Clock that is run by Cs133 Electrons, the Electrons are jumping forward and backward but are NOT reversing in 'time'/Events-Actions. Even when something or someone is walking backwards, they are STILL going forward.

Ah yes, an individual that doesn't understand gravity telling scientists what is or isn't possible.

Always interesting when a time asymmetry is proven. This one has been conjectured for a long time and it's good to see it confirmed. We can add this to the B-, D-, and k-mesons (also called kaons) as an example of broken time-reversal symmetry, and since it's in the EM force we can now see two of the four forces displaying time asymmetry: weak and EM. Interestingly, these two forces both originate from the electroweak force of Weinberg and Salam, indicating that we have much more to find out about this aspect of QM. There's new physics here somewhere.

@Da SchneibIt is always nice to read your knowledgeable posts. Like a swan in a quivering duck pond, you have a higher perspective and look over the reeds.

@QuantusYet, all he sees, is up his ass. That's right, Da Schitebo, is all neck, no swan.

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